Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
FILTER ELEMENT WITH CONDUCTIVE BREAKING INDICATOR
Document Type and Number:
WIPO Patent Application WO/2017/005969
Kind Code:
A1
Abstract:
A filter element, comprising a porous membrane layer constituting a suction wall of said filter element, the filter element further comprising at least one indicator extending along the filter element to form a continuous circuit and arranged to break upon breakage of the filter element. The breaking strength of the indicator is in range of 50 grams to 100 kg.

Inventors:
VESALA ANTTI (FI)
ILLI MIKA (FI)
VÄNTTINEN KARI (FI)
Application Number:
PCT/FI2016/050477
Publication Date:
January 12, 2017
Filing Date:
June 29, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
OUTOTEC FINLAND OY (FI)
International Classes:
B01D33/15; B01D33/21; B01D33/23; B01D35/143
Domestic Patent References:
WO2014170532A12014-10-23
WO2012102662A12012-08-02
Foreign References:
US20070044656A12007-03-01
US3358836A1967-12-19
Other References:
None
Attorney, Agent or Firm:
KOLSTER OY AB (FI)
Download PDF:
Claims:
CLAIMS

1 . A filter element, comprising a porous membrane layer constituting a suction wall of said filter element, the filter element further comprising

at least one indicator extending along the filter element to form a continuous circuit and arranged to break upon breakage of the filter element, the breaking strength of the indicator being in range of 50 grams to

100 kg. 2. The filter element according to claim 1 , wherein the breaking strength of the indicator is in range of 50 grams to 20 kg.

3. The filter element according to claim 1 , wherein the breaking strength of the indicator is in range of 50 grams to 5 kg.

4. The filter element according to claim 1 , wherein the breaking strength of the indicator is at least 100 grams.

5. The filter element according to any one of the preceding claims, being a sector-shaped filter plate of a disc filter apparatus.

6. The filter element according to any one of claims 1 - 4, being a filter plate of a drum filter apparatus. 7. The filter element according to any one of the preceding claims, wherein at least a portion of the indicator is arranged on/in a suction wall of the filter element.

8. The filter element according to any one of the preceding claims, wherein at least a portion of the indicator is arranged between the membrane layer and a substrate supporting the membrane layer.

9. The filter element according to any one of the preceding claims, wherein at least a portion of the indicator is arranged on/in the peripheral edge surface of the filter element.

10. The filter element according to any one of the preceding claims, wherein the indicator is of acid-proof material, preferably platinum or palladium composition. 1 1 . The filter element according to any one of claims 1 - 9, wherein the indicator is of non-acid-proof material provided with an acid-proof coating.

12. The filter element according to any one of the preceding claims, wherein the indicator comprises an electrically conductive layer.

13. The filter element according to claim 12, wherein the indicator comprises an electrically conductive wire.

14. The filter element according to any one of the preceding claims, wherein the porous membrane layer is a microporous membrane layer.

15. The filter element according to any one of the preceding claims, wherein the porous membrane layer is a porous ceramic membrane layer. 16. The filter element according to any one of claims 1 - 14, wherein the porous membrane layer is a porous polymer membrane layer.

Description:
FILTER ELEMENT WITH CONDUCTIVE BREAKING INDICATOR

Background

The invention relates to filter elements comprising a porous membrane layer.

Filtration is a widely used process whereby a slurry or solid liquid mixture is forced through a media, with the solids retained on the media, as a cake, and the liquid phase passing through. This process is generally well understood in the industry. Examples of filtration types include depth filtration, pressure and vacuum filtration, and gravity and centrifugal filtration.

The cake formation in vacuum filtration is based on generating suction within the filtrate channels. The most commonly used filter media for vacuum filters are filter cloths and coated media, e.g. the ceramic filter medium. These filter media are commonly used in filter apparatuses having filter comprising multiple filter elements, e.g. in rotary vacuum disc filters and rotary vac- uum drum filters.

Rotary vacuum disc filters are used for the filtration of relatively free filtering suspensions on a large scale, such as the dewatering of mineral concentrates. The dewatering of mineral concentrates requires large capacity in addition to producing a cake with low moisture content. Such large processes are commonly energy intensive and means to lower the specific energy consumption are needed. The vacuum disc filter may comprise a plurality of filter discs arranged in line co-axially and around a central pipe or shaft. Each filter disc may be formed of a number of individual filter elements or sectors, called filter plates, that are mounted circumferentially in a radial plane around the central pipe or shaft to form the filter disc, and as the shaft is fitted so as to revolve, each filter plate or sector is, in its turn, displaced into a slurry basin and further, as the shaft of rotation revolves, rises out of the basin. When the filter medium is submerged in the slurry basin where, under the influence of the vacuum, the cake forms onto the medium. Once the filter sector or plate comes out of the basin, the pores are emptied as the cake is deliquored for a predetermined time which is essentially limited by the rotation speed of the disc. The cake can be discharged by a back-pulse of air or by scraping, after which the cycle begins again. Whereas the use of a cloth filter medium requires heavy duty vacuum pumps, due to vacuum losses through the cloth during cake deliquoring, the ceramic filter medium, when wetted, does not allow air to pass through which does not allow air to pass through, which further decreases the necessary vacuum level, enables the use of smaller vacuum pumps and, consequently, yields significant energy savings.

Rotary vacuum drum filters are used for the filtration of relatively free filtering suspensions on a large scale, such as the dewatering of mineral concentrates. The dewatering of mineral concentrates requires large capacity in addition to producing a cake with low moisture content. The vacuum drum filter may comprise a cylindrical support structure rotating around a longitudinal shaft forming a centre axis for the drum. There is plurality of filter elements or plates arranged on the outer surface of the cylinder. Usually the filter elements are made of coated media, e.g. the ceramic filter medium. Each filter plate forms a portion of the cylindrical outer surface of the cylinder. Each filter plate is during each revolution of the shaft displaced for a certain period into a slurry basin situated below the shaft. The filter plate rises out of the basin when the revolution of the shaft proceeds. When the filter plate is submerged in the slurry basin, a cake forms onto the outer surface of the filter plate due to the vacuum within the filter plate. Once the filter plate comes out of the basin, the pores are emptied as the cake is deliquored for a predetermined time which is essentially limited by the rotation speed of the drum. The cake can be discharged by a back- pulse of air or by scraping, after which the cycle begins again. The filter elements of rotary vacuum drum filters are advantageously made of porous ceramic.

The filter elements are affected by slurry particles and extraneous compounds, especially in the field of dewatering of mineral concentrates. Filter element breakages happen once a while in operation when the filter elements are old, something gets stuck to scrapers or for some other reason. Broken ceramic element has to be removed because there is a significant risk that breakage of one element causes domino effect as the pieces of the broken element may break neighbouring filter plates etc, which may lead to a massive consequential damage of broken plates, and the filter apparatus is out of operation for many days.

Breakages of ceramic filter plate happen once a while in operation when the filter plates are old, something gets stuck to scrapers or for some other reason. There is a significant risk that breakage of one plate causes domino effect as the pieces of the broken plate may break neighbouring filter plates etc, which may lead to a massive consequential damage of broken plates, and the filter is out of operation for many days. In the worst case the consequential damage might cost hundreds of thousands of dollars for the user due to cost of the filter plates and the shutdown time of the process. Therefore, there is a need for detecting the breakage of filter plate prior to the con- sequential damage.

Brief description

Viewed from a first aspect, there can be provided a filter element, comprising a porous membrane layer constituting a suction wall of said filter element, the filter element further comprising at least one indicator extending along the filter element to form a continuous circuit and arranged to break upon breakage of the filter element, wherein the breaking strength of the indicator is in range of 50 grams to 100 kg.

Thereby a filter element and especially a break indicator which stands well stresses caused by the filtering process, but will broke in the scraper with breaking filter element may be achieved.

Some other embodiments are characterised by what is stated in the claims. Inventive embodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub- tasks or in view of obtained benefits or benefit groups. Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments.

Brief description of figures

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which

Figure 1 is a perspective top view of an exemplary disc filter apparatus,

Figure 2 is a perspective top view of a second exemplary drum filter apparatus,

Figure 3a illustrates a filter element,

Figure 3b is a side view of an embodiment of the filter element shown in Figure 3a,

Figure 3c is a side view of another embodiment of the filter element shown in Figure 3a,

Figure 4a illustrates a second filter element,

Figure 4b is a cross-section view of the filter element shown in Figure 4a,

Figure 5a illustrates a third filter element,

Figure 5b is a side view of the filter element shown in Figure 5a, Figure 6a illustrates a fourth filter element,

Figure 6b is a side view of the filter element shown in Figure 6a, and

Figure 7 illustrates a fifth filter element.

In the figures, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures. Detailed description

Figure 1 is a perspective top view of an exemplary disc filter apparatus 1 . In the disc filter apparatus 1 , the actual filter 2 comprises at least one filter disc 3, each of which comprises number of sector-shaped filter elements 4 that are mounted circumferentially in a radial planar plane around the central axis of the disc filter apparatus 1 . The number of the filter elements 3 included in a filter disc may be 12 or 15, for example.

The structure of the filter elements 3 is decribed more detailed later in this description.

As the filter disc 3 rotate, each filter element 4 is, in its turn, dis- placed into a slurry basin and further, as the rotation continues, rises out of the basin.

Filter element breakages happen once a while in operation when the filter elements 4 are old, something gets stuck to scrapers that scraped the material cake off from the filter element 4, or for some other reason. There is a significant risk that breakage of one plate causes domino effect as the pieces of the broken plate may break neighbouring filter plates etc, which may lead to massive consequential damage of broken elements, and filters is out of operation for many days.

Figure 2 is a perspective top view of an exemplary drum filter appa- ratus. The filter apparatus 1 may comprise a filter drum 1 1 , i.e. the filter apparatus is a drum filter apparatus. In the drum filter apparatus 1 the filter element 3 is a part of outer surface of the filter drum 1 1 . The diameter of the filter drum 1 1 may be e.g. in range of 1 .8 m - 4.8 m and length in axial direction 1 m - 10 m. The surface area of the filter may be e.g. in range of 2 - 200 m 2 .

Examples of commercially available drum filters include CDF-6/1 .8 manufactured by Outotec Inc.

Figure 3a illustrates a filter element of a disc filter apparatus, and Figure 3b is a side view of the filter element shown in Figure 3a.

The filter element 3 may comprise a suction wall 6a and an opposed second suction wall 6b.

The suction walls 6a, 6b may comprise a porous membrane 7 and a substrate 8, whereon the membrane 7 is positioned.

An interior space may defined between the opposed first and sec- ond suction walls 6a, 6b resulting in a sandwich structure. The interior space provides a flow canal or canals where a negative pressure is maintained, i.e. a pressure difference is maintained over the suction wall.

The material of the porous membrane 7 may be e.g. ceramics or polymer and the substrate 8 may made of be e.g. ceramics or polymer.

The membrane 7 may contain micropores that create strong capillary action in contact with water. This microporous filter medium allows only liquid to flow through. Filtrate is drawn through the suction walls 6a, 6b as the filter element 4 is immersed into the slurry to be filtered, and a cake of solid particulate material forms on the suction walls 6a, 6b.

According to an aspect, the filter element 4 is provided with at least one indicator 5 extending along the filter element 4 to form a continuous circuit and arranged to break upon breakage of the filter element 4.

In an embodiment, the indicator 5 comprises an electrically conductive layer, e.g. a printed electric wire, a casted electric wire, a microstrip line, separate electric wire, a metal tape or a painted electric circuit, for example.

In the embodiment shown in Figure 3a, the indicator 5 is arranged along the peripheral edge surface 9 of the filter element 4. The indicator 5 can be coated with an acid-proof coating, such as epoxy based painting or enamel.

Therefore, in embodiments based on electrically conductive layers, cheaper materials (such as copper tape) which are not acid-proof can be used.

Alternatively, the electrically conductive indicator 5 is made of acid- proof material, e.g. platinum or palladium or compositions thereof are especially advantageous materials for implementing acid-proof wiring. The indicator 5 made of acid-proof material may be arranged on the surface of the filter element 4, such as the peripheral edge surface 9, by e.g. gluing and without any coating.

It is to be noted, that additional protecting layer covering the indicator 5 may be required against the direct mechanical and chemical stress from the from the process environment.

In an embodiment, the indicator 5 is arranged inside the material of the filter element 4. For instance, the indicator 5 may be arranged in a mould used in manufacturing of the filter element so that the indicator 5 remains in the material curing in the mould. Alternatively, in case the filter element or at least part of it is manufactured by pressing, the indicator 5 is arranged among the granules to be pressed.

In an embodiment, the breaking strength of the indicator 5 is in range of 50 grams to 100 kg. This kind of conductor stands well stresses caused by the filtering process, but will broke in the scraper with breaking filter element 3.

In an embodiment, the breaking strength of the indicator 5 is in range of 50 grams to 20 kg. This kind of conductor will broke in the scraper without any risk for breaking the scraper.

In an embodiment, the breaking strength of the indicator 5 is in range of 50 grams to 5 kg. This kind of conductor will break already in cracking of the filter element 3. Thus the malfunction of the filter element 3 can be de- tected at early stage, e.g. suction of air through the suction wall can be minimized or avoided. Suction of air will cause remarkable waste of energy in the filtering process.

In an embodiment, the breaking strength of the indicator 5 is at least 100 grams. This kind of conductor stands well fluctuations of the process caused by silt and deposit accumulating in the slurry basin.

The integrity of the conductive wiring is monitored, and the operation, particularly the rotation, of the disc filter apparatus is immediately stopped in response to detecting a break of one of the conductive wirings. This action will advantageously save all the other plates of the disc filter from getting bro- ken. Operation downtime decreases as the consequential damage of several broken plates is avoided and the operator of the disc filter can concentrate on displacing the broken plate. The number of broken consumed filter plates decreases which results in lower operational costs.

Figure 3c is a side view of another embodiment of the filter element shown in Figure 3a. This embodiment differs from the embodiment shown in Figure 3b in that, instead of one indicator 5, there are two indicators 5 on the peripheral edge surface 9 of the filter element 4. The two indicators 5 are arranged close to the edges of the filter element 4. Thus, the sensitivity of the indicators 5 to breakages taking place in the suction wall 6a, 6b may be enhanced.

Figure 4a illustrates a second filter element and Figure 4b is a cross-section view of the filter element shown in Figure 4a.

In this embodiment, the indicator 5 is provided between substrate 8 and the membrane 7 on the both sides of the filter element 4.

In this case the membrane 7 protects the indicator 5 against the di- rect mechanical and chemical stress from the from the process environment.

However, the indicator 5 is preferably made of acid-proof material, advantageously of platinum or palladium or compositions thereof. The indicator 5 may be manufactured by, for example, applying (preferably printing) a pattern of conductive paste on the outer surface of the substrate 8 prior to making the membrane layer 7. This approach can also detect a stripping of the membrane prior to an actual breakage of the substrate.

Strength of the indicator 5 may vary as disclosed above in description of Figures 3a - 3c.

Figure 5a illustrates a third filter element and Figure 5b is a side view of the filter element shown in Figure 5a.

In this embodiment, the indicator 5 is provided mainly on the peripheral edge surface 9, but a portion thereof is arranged in/on the suction wall 6a near the end of the of the filter element 4. Said portion may be arranged on sections of the suction wall 6a which are not scraped by the scrapers of the disc filter apparatus 1 . Alternatively, said portion may be arranged between substrate and the membrane of the suction wall.

In another embodiment, there is also another indicator 5 a portion of which is arranged in/on the second suction wall 6b.

The materials of the indicator 5 may be selected as described above in description of Figures 3a - 3c. Furthermore, the indicator may be arranged on the surfaces of the filter element 4 or embedded into the material of the pe- ripheral edge surface and/or the suction wall.

Strength of the indicator 5 may vary as disclosed above in description of Figures 3a - 3c.

Figure 6a illustrates a fourth filter element, and Figure 6b is a side view of the filter element shown in Figure 6a.

Also in this embodiment, the indicator 5 is provided mainly on the peripheral edge surface 9, but a portion thereof is arranged in/on the suction wall 6a near the attachment means 10 of the of the filter element 4. Said portion may be arranged on sections of the suction wall 6a which are not scraped by the scrapers of the disc filter apparatus 1 . Alternatively, said portion may be arranged between substrate and the membrane of the suction wall.

In another embodiment, there is also another indicator 5 a portion of which is arranged in/on the second suction wall 6b near the near the attachment means 10.

The materials of the indicator 5 may be selected as described above in description of Figures 3a - 3c. Furthermore, the indicator may be arranged on the surfaces of the filter element 4 or embedded into the material of the peripheral edge surface and/or the suction wall. Strength of the indicator 5 may vary as disclosed above in description of Figures 3a - 3c.

Figure 7 illustrates a fifth filter element. The principles of the aspects and embodiments described above in connection with Figures 3a - 6b may also be applied to ceramic filter elements of drum filter apparatuses.

The main difference of the filter elements of drum filters compared to the filter elements of disc filters is that the latter typically has suction walls on both sides of the filter element, whereas the filter elements of drum filter typically has one suction wall only, on its outer surface. Furthermore, the elements of drum filters have typically rectangular shape as shown in Figure 7.

The invention is not limited solely to the embodiments described above, but instead many variations are possible within the scope of the in- ventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conjunction with or replace the attributes of another embodiment or application.

The drawings and the related description are only intended to illus- trate the idea of the invention. The invention may vary in detail within the scope of the inventive idea defined in the following claims. Reference symbols

1 filter apparatus

2 filter

3 filter disc

4 filter element

5 indicator

6a, 6b suction wall

7 membrane layer

8 substrate

9 peripheral edge surface

10 attachment means

1 1 filter drum